Patent Grant
7683867
This application claims priority of Japanese Patent Application No.: 2005-18326, filed on Jan. 26, 2005, and entitled, “Information Processing Apparatus, Method of Controlling Display of Liquid Crystal Display, Program Product for Executing Method of Controlling Display, and Information Processing Apparatus with Improved Adjustment Effects on Viewing Angle Range.”
1. Technical Field
The present invention relates to a technique of controlling viewing angle characteristics of a liquid crystal display, and more particularly to an information processing apparatus, a method of controlling a display of a liquid crystal display, and a program for executing the method of controlling the display that provide a narrow viewing angle characteristic by controlling gradation of the liquid crystal display.
2. Description of Related Art
A liquid crystal display is used for an information processing apparatus, such as a laptop computer, a notebook computer, a PDA, and a mobile phone in many cases to thereby provide a display to a user. Particularly, in recent years, due to downsizing of the information processing apparatus, the information processing apparatus is increasingly used under a situation where persons other than the user are present within easy reach. Especially, information displayed on the liquid crystal display of a portable information processing apparatus includes privacy information in many cases, and therefore preferably the persons other than the user are prevented from being able to recognize the information.
Various kinds of methods for controlling a viewing angle in the liquid crystal display have been disclosed so far. For example, in Japanese Unexamined Patent Publication (Kokai) No. 2003-295160, there is disclosed a liquid crystal display in which high contrast is provided even in a wide viewing angle by adjusting distortion due to a viewing angle of a gradation curve on a display screen, and on the contrary, by providing a display image with an narrow viewing angle, information that user does not want to be seen by others is displayed. In Japanese Unexamined Patent Publication (Kokai) No. 2003-131230, there is disclosed a display unit that obtains a narrow viewing angle characteristic by using a prism sheet almost meeting with an optical property in a viewing angle being narrowed. Moreover, in Japanese Unexamined Patent Publication (Kokai) No. 2004-318112, there is disclosed a liquid crystal display provided with a look-up table for controlling a driving voltage supplied to a liquid crystal panel for the purpose of providing a narrow viewing angle. Furthermore, in Rocket_SecurityShades, there is employed a method of controlling the viewing angle, in which a display gradation range is narrowed by not using gradation levels at both sides of higher gradation levels and lower gradation levels for the display, to thereby reduce visibility with respect to a large viewing angle.
According to the method disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2003-295160, in order to adjust the distortion due to the viewing angle of the gradation curve, there is employed the method, in which a plurality of look-up tables to be referenced are prepared, and one pixel is further divided into a plurality of sub-pixels to thereby provide different gradation curves to respective sub-pixels. For this reason, according to the method disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2003-295160, there has been such inconvenience that a configuration of a liquid crystal display panel has needed to be changed significantly, and in addition to that, contrast characteristics with respect to the viewing angle might not be necessarily controlled sufficiently.
Meanwhile, according to achieving the narrow viewing angle using the prism sheet described in Japanese Unexamined Patent Publication (Kokai) No. 2003-131230, a configuration of an LCD panel needs to be changed, for example, by preparing the prism sheets with different dimensions or the like for respective LCD panels. Additionally, in the liquid crystal display for controlling the driving voltage of the LCD to provide the narrow viewing angle disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2004-318112, in attempting to achieve the narrow viewing angle, there is employed the method of generating a gradation collapse in a diagonal viewing angle by increasing the driving voltage on a low gradation side. According to the method disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2004-318112, in order to control the driving of the liquid crystal display, it is necessary to change the driving voltage of the LCD panel, so that there is such an inconvenience that flexibility to the liquid crystal display cannot be obtained, for example a dedicated driver for LCD is required.
Furthermore, also in the conventional art described in Rocket_SecurityShades, since the narrow viewing angle has been achieved by only reducing a gradation width to be displayed, contrast has wholly been decreased, so that there has been such an inconvenience that contrast at the time of being seen from the front has been decreased. Additionally, according to the method described in Rocket_SecurityShades, even when the LCD panel is seen from the large viewing angle, a displayed image will be visible to some extent, so that there is such an inconvenience that good privacy protection cannot necessarily be provided to the user.
Other than this, in order to narrow the viewing angle, there has been employed a method of pasting a film formed into a louver structure, the so-called privacy filter on the liquid crystal display panel or the like. However, this causes other problems, in that the user needs to purchase the privacy filter, mounting the privacy filter has been troublesome, the viewing angle has not been dynamically controllable in response to a user's request, brightness has been reduced, a film exchange has been required because of durability of the film, or the like, so that the method has not been able to provide sufficient visibility and permanency.
In view of the problems of the aforementioned conventional art, the present invention aims at improving adjustment effects on a viewing angle range by providing a steeper change in curve than before as to the viewing angle from a small viewing angle (front direction) to a large viewing angle (slant direction) with respect to a change in contrast according to a user's viewing angle to an LCD panel.
Moreover, the present invention aims at providing an information processing apparatus, a display control method, and a program for the same that can provide a curve with a steeper change in contrast than before against the aforementioned viewing angle.
As a result of the present inventors' earnest studies to solve the problems associated with the aforementioned conventional art, in an LCD panel in a TN (twisted nematic) mode, particularly when the user's viewing angle (here, viewing angle=an angle measured from a perpendicular to the screen of the LCD panel) has been large, the present inventors have found that a linearity between brightness and gradation level is abruptly lost particularly in a region where gradation levels are low, whereby the present invention has been made.
More specifically, according to the present invention, a liquid crystal display in the TN mode is provided with a color conversion table corresponding to color palette data with gradation levels lower than predetermined gradation levels for the predetermined gradation levels, wherein in response to a user's instruction, the color conversion table to be used is switched from a color conversion table in the normal mode to a reduced-color conversion table to which a narrow viewing field displaying mode is applied. For example, if N is the number of display gradations and M is a reduction factor, the reduced-color conversion table may be stored in an appropriate storage area of the information processing apparatus as a data structure, in which, for example, the color palette data provided by N/M are allocated to a plurality of the N/M gradations from gradation level 0 through (N-M) level. As a result of this, a color conversion with the color palette data of the N/M gradations is performed, for example, from the original N gradation to the N/M gradations. Here, N and M are positive integers: N normally has the value of a power of 2, such as 64 or 256, and M can be selected from integers smaller than N. In addition, according to the present invention, as for the reduction factor, each of the gradation levels of the number of display gradations N does not need to have the same reduction factor, but it may be appropriately changed according to an application and a specific embodiment. The color palette data may be reduced so that, for example, an M-fold reduction is achieved from the gradation level N-1 to the gradation level (N-A), and an L-fold reduction is achieved from the next (N-A-1) to (N-A-B).
According to a preferred embodiment of the present invention, the reduced-color conversion table may have a data structure where, for example, when the viewing angle is large, higher gradations among the N gradations are associated with the color palette data of the lower gradations whose linearity between brightness and gradation level is lost, sequentially from the highest gradation. In other words, according to the present invention, visibility in a position where the viewing angle is large is reduced not by cutting the display gradations, but by utilizing a decrease in linearity between brightness and gradation level in the low gradations with the use of the reduced-color conversion table which is reduced so that the number of gradations may be N/M.
According to the aforementioned configuration of the present invention, as compared with the visibility control with respect to the conventional viewing angle, it is possible to provide a contrast curve having a higher peak to a front direction than that of the conventional way. As a result of this, it is possible to provide an information processing apparatus and a display control method, which can reduce the visibility in the large viewing angle with hardly affecting the visibility in the front direction, and use the LCD panel driven in the TN mode across wide ranges of viewing angle, and a program which causes the information processing apparatus to execute this display control method.
Thus, the information processing apparatus according to the present invention includes second software that receives a display mode changing instruction to pass a display control of an LCD panel to first software from the CPU 12 and a plurality of display control tables 38, in which color palette data of 128 or less gradation levels are reduced and allocated to higher gradation levels, wherein a reduced-color conversion table associated with a corresponding identification data is searched for from identification data of the LCD panel obtained by the first software to which the control is passed or the second software. A display adapter 30 reads out the reduced-color conversion table searched for from a display control table storing section 36 to a look-up table (LUT) reading section 40, and generates an RGB signal with reduced gradations.
Hereinafter, the present invention will be explained using embodiments shown in the drawings, but the present invention is not limited to the embodiments described herein below.
The above, as well as additional purposes, features, and advantages of the present invention will become apparent in the following detailed written description.
The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further purposes and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, where:
a-b are diagrams showing an embodiment of a display control table according to the present invention;
a-b are illustrations showing a storage mode of a color conversion table and a reduced-color conversion table according to the present invention;
A display unit 28 provided with an LCD panel is further connected to the information processing apparatus 10, whereby the display unit 28 receives a video signal from the CPU 12 and the memory 16 via a display adapter 30 in the information processing apparatus 10 and then performs an RGB display on the LCD panel. The information processing apparatus 10 according to the present invention may be a portable laptop computer or notebook computer in particular, a mobile phone, or a PDA, and the display unit 28, in the case of the laptop computer or the notebook computer, is openably and closably attached to the information processing apparatus 10. Meanwhile, when the present invention is incorporated in the mobile phone or a PDA, it may be integrated with the information processing apparatus 10. It should be noted that the LCD panel according to the present invention is an LCD panel that operates in a twisted nematic (TN) mode.
More specifically, the display adapter 30 includes a graphics engine 32 which is a CPU for executing rendering processing, a video memory (frame buffer for image) 34 for temporarily storing an frame image processed by the graphics engine 32 until it is displayed, and in a specific embodiment according to the present invention, a look-up table (LUT) reading section 40 for reading a display control table 38 composed of a reduced-color conversion table and a color conversion table stored in a display control table storing section 36 including an erasable memory device, such as an EEPROM, flash memory, or the like, to thereby generate RGB data to be displayed. The look-up table (LUT) reading section 40 generates the RGB data to be displayed, with reference to the display control table 38 having been read. Generated RGB data are sent to the display unit 28 to display an RGB image on the LCD panel.
According to the present invention, the display control table 38 has a data structure including a reduced-color conversion table for normal mode, and one or more types of reduced-color conversion tables for narrow viewing field displaying mode, for every identification data for specifying a type of the display unit 28 to be connected, where a plurality of tables are prepared associated with the types of the corresponding LCD panel. Moreover, as for the reduced-color conversion tables included in the display control table 38, as will be described later in the present invention, it is also possible to prepare two or more types of reduced-color conversion tables, which correspond to the viewing angle control according to a plurality of gradation levels and are different in reduction factors for every predetermined LCD panel. Upon receiving a user's instruction to select the narrow viewing field displaying mode via a utility software allocated to a function key or a dedicated button, the CPU 12 activates the BIOS to pass control of the display unit to a display device driver which will be described later, and selects the corresponding display control table 38 with reference to the identification data of the display unit 28. A selected reduced-color conversion table is read by the look-up table (LUT) reading section 40, and RGB data are generated with reference to the reduced-color conversion table.
Moreover, according to another embodiment of the present invention, when it is intended that the display control method according to the present invention is included in a manufacturing stage of the information processing apparatus, the reduced-color conversion table may be stored in a reduced-color conversion table storing section, which is provided apart from the color conversion table in the normal mode and composed of a memory, such as a ROM, EEPROM, or the like. In this case, when there is a display mode switching instruction from the user, the display device driver can provide the reduced-color conversion table to the display control table storing section 36 of the display adapter 30 shown in
The aforementioned application software 42 includes not only word processor software, mail software, or the like, but also database software, various kinds of utility software, or the like. Meanwhile, the operating system includes not only various kinds of operating systems beginning with Windows (registered trademark), but also operating systems, such as MacOS™, OS/2, or the like, which are used for a laptop and notebook PC, a mobile phone, or a PDA.
In addition, according to the present invention, the device drivers 44 through 48 may be included as a software module of the operating system. In this case, the reduced-color conversion table used in the present invention may be stored in the reduced-color conversion table storing section provided by securing an appropriate memory in the system. Moreover, according to the present invention, as the program for executing the narrow viewing field displaying mode of the present invention, software different from the operating system may be used. When the software different from the operating system is provided as the program for executing the display method of the present invention, the user independently prepares device driver software for the present invention to install it in the information processing apparatus, thereby making it possible to incorporate the above software in the information processing apparatus. In this case, the reduced-color conversion table is first stored in a hard disk along with the display device driver, and then transferred to be stored in the memory 16 or the like at the time of activation, and in response to the user's instruction, read to the look-up table (LUT) reading section 40.
Further, the device drivers 44 through 48 control hardware devices 50 through 54 shown by the broken line in
In the specific embodiment according to the present invention shown in
Meanwhile, an embodiment of the reduced-color conversion table 38a illustrated in
In the embodiment illustrated in
In the normal mode, the Video BIOS selects the color conversion table of the normal mode stored in the memory area 60 as the color conversion table used by the graphics engine 32, and passes the selected color conversion table to the look-up table (LUT) reading section 40, so that the display control in the normal mode is executed. Meanwhile, when receiving an instruction to display in the narrow viewing field displaying mode from the display device driver 48, the Video BIOS changes a read address area to the memory area 62, selects the reduced-color conversion table corresponding to the instructed identification data, the optimal number of display gradations, or the like, and passes it to the look-up table (LUT) reading section 40, so that the display control in the narrow viewing field displaying mode is executed.
Meanwhile, in the embodiment shown in
A twisted nematic (TN) display is a liquid-crystal display (LCD) that has two plates of polarized glass, between which is confined a substance called a nematic liquid crystal. The nematic liquid crystal rotates the polarization of light beams passing through it. Two polarizing filters (an input filter and an output filter), which are parallel planes of glass with their polarizing lines oriented at right angles with respect to each other, are positioned on either side of the nematic liquid crystal. When light enters the TN display, the light is polarized by the input filter. In the absence of an electric field, all the incoming light is passes through the TN display. This is because the light polarization is rotated 90 degrees by the nematic liquid crystal, and the light therefore passes easily through the output filter, which is oriented to match the 90-degree shift. With the application of a voltage, an electric field is produced in the nematic liquid crystal. Under these conditions the polarization effect is reduced. If the voltage is large enough, the polarization effect disappears altogether, and the light is blocked by the output polarizing filter. Thus, the present invention, in a preferred embodiment, is directed to a display that uses a TN display, and thus display drivers are in “TN mode.”
Meanwhile, when the display mode changing instruction is allocated to a specific function key for the code of the display mode switching instruction of the present invention, an instruction on a display mode change is issued (YES) by a user's operation of depressing the specific function key, and the BIOS passes the control of the display unit to the display device driver at Step S104. Subsequently, at Step S106, the display device driver reads the identification data and the optimal number of display gradations of the LCD panel stored in, for example the ROM or the like from the memory device of the display unit or an appropriate memory area of the information processing apparatus.
Subsequently, at Step S108, by retrieving the reduced-color conversion tables 38a, which are stored in the BIOS with the identification data and the optimal number of display gradations obtained by the display device driver as keys or held as data by the display device driver, a corresponding reduced-color conversion table for the relevant LCD panel is selected. At Step S110, the selected reduced-color conversion table is read to the display adapter, and thereby an RGB signal corresponding to the narrow viewing field displaying mode is generated to display the image on the LCD panel.
Hereinafter, the present invention will be explained using an embodiment. Incidentally, an embodiment with 64 gradations will be explained.
Moreover, selecting curve C1 or curve C2 may provide different viewing angle restriction effects, thereby making it possible for the user to perform the optimal viewing angle adjustment depending on usage situations.
In
Meanwhile, in the method of controlling the display mode of Rocket_SecurityShades, it will be understood that even when the image is seen from the front, the contrast of the displayed image is considerably reduced to hardly be seen. Meanwhile, as will be understood, if the displays with the wide viewing angle are compared, the contrast is reversed in part, but the displayed image according to the present invention can be hardly read. According to the image obtained by the method of Rocket_SecurityShades, however, it is shown that when the image is seen from the front, although the contrast is reduced, the image can be read to some extent even when the viewing angle is wide.
The present invention may be used for the display control of, for example a laptop computer, a notebook computer, a PDA, a mobile phone, or the like, as far as it is a portable information processing apparatus using the liquid crystal panel driven in the TN mode. In addition, a program for causing the information processing apparatus to execute the display control method according to the present invention may be described using an object oriented programming language such as C and C++, or a non object-oriented programming language. Moreover, the display control method according to the present invention has so far been explained supposing that the display control is performed by the display device driver through the involvement of the BIOS, but all control may be performed by the BIOS, or all may be performed by the device driver. The method according to the present invention may be implemented by hardware using an LSI such as a graphics chip or the like, instead of software such as a device driver, thereby allowing more flexible viewing angle control to be provided.
It should be understood that at least some aspects of the present invention may alternatively be implemented in a computer-useable medium that contains a program product. Programs defining functions on the present invention can be delivered to a data storage system or a computer system via a variety of signal-bearing media, which include, without limitation, non-writable storage media (e.g., CD-ROM), writable storage media (e.g., hard disk drive, read/write CD ROM, optical media), and communication media, such as computer and telephone networks including Ethernet, the Internet, wireless networks, and like network systems. It should be understood, therefore, that such signal-bearing media when carrying or encoding computer readable instructions that direct method functions in the present invention, represent alternative embodiments of the present invention. Further, it is understood that the present invention may be implemented by a system having means in the form of hardware, software, or a combination of software and hardware as described herein or their equivalent.
As described above, according to the present invention, it is possible to provide the contrast curve that is versatilely applicable to the LCD panel in the TN mode, and in addition to that, has a peak particularly to a front direction as compared with the conventional visibility control to the viewing angle. Therefore, that makes it possible to reduce the visibility in the front direction across the large viewing angles, with hardly affecting the visibility, allowing an increase in the security to be achieved.
While the present invention has been explained using the embodiment shown in the drawings so far, the present invention is not limited to the embodiments shown in the drawings, but may be incorporated in the information processing apparatus as various improvements and modifications, and other embodiments.
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|---|---|---|---|
| 2005-018326 | Jan 2005 | JP | national |
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| Number | Date | Country | |
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